1. Field of the Invention
This invention relates, particularly, to venetian blinds having vertical louvers. More specifically, this invention relates to the pull carrier for such a vertical venetian blind, which pull carrier is utilized to transport the louver carriers to the left and the right in the axial direction of a drive shaft which passes through the louver carriers and the pull carrier, and which drive shaft has at least one helical groove.
Still more particularly, the invention relates to a pull carrier which during turning of the louvers about their vertical axes does not exert any lateral traversing action on the louver carriers associated with it.
2. Prior Art
Venetian blinds are well-known, which blinds may have either horizontal or vertical louvers. Blinds of the type having vertical louvers are known in which two drive shafts are provided. One drive shaft serves to rotate the louvers about their vertical axes while the other drive shaft serves to move the louvers left and right of the drive shaft to their closed or open position. Generally, in the opened position the louvers are arranged in two packs, one to the left and one to the right of the window. In their closed position, the two packs of louvers have been arranged substantially equidistantly across the window from left to right rather than in packs with one louver from the left pack and one louver from the right pack being positioned in predetermined spaced relationship to each other in the center of the window. Whether in open, closed, or any intermediate position, the blind must provide for rotation of the louvers about their vertical axes in order to adjust the amount of sunlight passing therethrough. In one position, the louvers are closed and overlap so that no sunlight and no viewing is possible through the window. At the other extreme, the planes of the louvers are arranged substantially perpendicular to the window, whereby there is almost no obstruction to prevent viewing or passage of sunlight. Accordingly, all vertical venetian blinds must be capable of lateral traverse and of vertical rotation about the axes of the individual louvers. While this has commonly been done by two separate drive shafts, there have been vertical blinds with a single drive shaft which performs both the function of rotating the louvers about their vertical axes and also the function of traversing the louvers laterally into packs at the sides, or evenly distributed across the window.
In many applications, the single drive shaft is preferred both for economy and ease of operation. The difficulty arises, however, that the blind must be so constructed as to avoid rotation of the louvers about their vertical axes during transport of the blind and also that traverse of the blind must not take place during rotation of the louvers about their vertical axes.
Heretofore it has been difficult, when using a single drive shaft, to insure that the two functions are adequately separated and do not overlap. Such difficulty has given rise to complicated and expensive mechanisms in order to insure proper operation.